Vehicle systems that include turbochargers typically utilize a wastegate, or wastegate valve, that functions to regulate boost pressure by routing excess exhaust gas around a turbine positioned in an exhaust system. More specifically, when boost pressure approaches a predetermined threshold pressure, or under conditions where there is a risk of turbine overspeed, the wastegate valve may be opened to channel exhaust directly toward a tailpipe, without imparting energy to the turbocharger. However, due to varying temperatures, and the constituents of the exhaust gas, such valves may accumulate a build-up of hydrocarbons, soot, and other compounds. Such build-up can in some examples result in the wastegate being stuck in a closed configuration, or an open configuration. A stuck closed wastegate may result in innacurate boosting engine overheating, turbine overspeed, etc. A stuck open wastegate may result in low boost, poor fuel economy and/or undesired emissions. Accordingly, under conditions where such symptoms are observed and/or indicated via vehicle diagnostics, diagnosing whether the indicated symptoms are the result of a stuck open or stuck closed wastegate may allow for mitigating actions to be undertaken quickly, which may prevent undesired degradation of the engine system.
One example approach for diagnosing whether a wastegate is functioning as desired is shown by Xinyu, G. E. in US 20160178470. Therein, a method includes defining a measurement window for performing sensor diagnostics, the measurement window occurring when a plurality of engine conditions fall within particular value ranges, identifying the measurement window during operation of the engine, collecting wastegate position data and sensor data within the measurement window, and via the use of a regression model, inferring a wastegate that is potentially not functioning as desired in response to an indication that a threshold number (e.g. 4) of sensors are indicated to be not functioning as desired. In other words, if the threshold number of sensors are not indicated to be functioning as desired, the likely culprit is not the sensors as it is unlikely that all should fail, but rather, that the wastegate is not functioning as desired.
However, the inventors have herein recognized potential issues with such an approach. Particularly with regard to hybrid electric vehicles, engine operation may be limited, and accordingly, there may rarely be opportunities where conditions satisfying the measurement window are indicated to be met, thus limiting opportunities to diagnose the wastegate. Under conditions where the wastegate is not functioning as desired, but where conditions are not met for conducting the diagnostic for a period of time, any engine operation may result in degradation of engine components. Furthermore, reliance on a regression model may be prone to error, as the engine and its components age and become susceptible to degradation. Accordingly, another method that may be particularly useful for hybrid vehicles, is desired.
In one example, the issues described above may be addressed by a method comprising activating an electric air compressor in an intake of an engine and monitoring air flow in an exhaust system of the engine to obtain a first and a second baseline air flow, and during a degradation test, the degradation test requested responsive to an indication of engine degradation, diagnosing whether a wastegate in the exhaust system is functioning as desired by activating the electric air compressor and comparing a test air flow in the exhaust system to the first and/or the second baseline air flow. In this way, the wastegate may be diagnosed under conditions where engine operation is limited, such as is the case for hybrid electric vehicles.
As an example of the method, just prior to activating the air compressor to obtain the first baseline air flow, the second baseline air flow, and just prior to diagnosing whether the wastegate is functioning as desired, the method may include controlling the engine via a motor to a predetermined position, where the predetermined position includes a predetermined piston coupled to a predetermined cylinder of the engine within a threshold number of degrees from top dead center.
As another example of the method, obtaining the first and the second baseline air flow, and diagnosing whether the wastegate is functioning as desired may include monitoring air flow in the exhaust system of the engine with an exhaust gas recirculation valve positioned in an exhaust gas recirculation passage for a predetermined duration with the exhaust gas recirculation valve closed, then monitoring air flow in the exhaust system of the engine with the exhaust gas recirculation valve open, and obtaining a difference between air flow with the exhaust gas recirculation valve open compared to air flow with the exhaust gas recirculation valve closed to provide the first baseline flow, the second baseline air flow, or the test flow. In some examples, the first baseline air flow, the second baseline air flow, and the test air flow is monitored via a differential pressure sensor positioned in an exhaust system downstream of a turbine. As one example, the differential pressure sensor may be coupled to a gasoline particulate filter.
As another example of the method, the first baseline air flow may be obtained with the wastegate commanded to a fully closed configuration, and the second baseline air flow may be obtained with the wastegate commanded to a fully open configuration. In such an example, the test air flow may be obtained via commanding the wastegate to the fully open configuration under conditions where the indication of engine degradation includes an indication that the wastegate is stuck closed, and wherein the test air flow may be obtained via commanding the wastegate to the fully closed configuration under conditions where the indication of engine degradation includes an indication that the wastegate is stuck open. Accordingly, diagnosing whether the wastegate is functioning as desired may thus include indicating the wastegate is stuck closed responsive to the test air flow under conditions where the wastegate is commanded to the fully open configuration being within a threshold of the first baseline air flow, and indicating the wastegate is stuck open responsive to the test air flow under conditions where the wastegate is commanded to the fully closed configuration being within a threshold of the second baseline air flow.
By diagnosing the wastegate in vehicles where engine run-time may be limited, potential issues related to engine degradation may be indicated and mitigating actions may be taken, such that such engine degradation may be reduced or avoided.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.